A Web application (Web app) is an application program that is stored on a remote server and delivered over the Internet through a browser interface. (from WhatIs.com)

Web (application) framework

A Web framework is a collection of packages or modules which allow developers to write Web applications or services without having to handle such low-level details as protocols, sockets or process/thread management. (from PythonWiki)

Front-end web development

Front-end web development, also known as client-side development is the practice of producing HTML, CSS and JavaScript for a website or web application so that a user can see and interact with them directly. (from Wiki)

Back-end web development

Back-end web development creates the logical back-end and core computational logic of a website. (from techopedia)